Today, mobile terminals such as mobile phones and personal digital assistants (PDA) are in widespread use. Reasons for the widespread use of the mobile terminals include the fact that they are easy to carry and have a variety of functions.
However, since the mobile terminals have a variety of functions, there are cases where a built-in memory is not sufficient to secure necessary data. Consequently, it has become common that many of the mobile terminals of today are equipped with an external memory in which data is saved.
There are such external memories as SD memory cards, mini SD cards, smart SDs, Memory Sticks, Smart Media, MMC memory cards, CompactFlash® memories, Microdrives, and compact HHDs. In the following description, an SD memory card is used as an example of the external memories.
FIG. 1 is a diagram showing a hardware configuration of a conventional mobile terminal. This mobile terminal 200 includes a ROM 203, a RAM 202, a CPU 201, an SD slot 204, and other functional units 205.
The ROM 203 stores programs. The RAM 202 temporarily stores data which is to be used when a program is executed. The CPU 201 performs various processing such as control processing, in accordance with programs stored in the ROM 203. The SD slot 204 is a slot in which an SD memory card is inserted. The other functional units 205 are, for example, EEPROMS, which are used for implementing other functions.
FIG. 2 is a diagram showing a software configuration of the conventional mobile terminal. The mobile terminal 200 includes, as its functions, an SD slot status detecting unit 304, an electric power supplying unit 302, a recognition processing unit 303, and a controlling unit 301.
The SD slot status detecting unit 304 detects that an SD memory card is inserted. The electric power supplying unit 302 supplies electric power to the SD memory card. The recognition processing unit 303 sends and receives a predetermined command for recognizing the SD memory card. The controlling unit 301 controls the electric power supplying unit 302 and the recognition processing unit 303.
FIG. 3 is a flowchart showing processing in which the conventional mobile terminal recognizes the SD memory card. First, when detecting that a card is inserted into the SD slot (Y in S601), the SD slot status detecting unit 304 notifies the controlling unit 301 of the detection. The controlling unit 301 instructs the electric power supplying unit 302 to start supplying electric power to the SD memory card (S602), and instructs the recognition processing unit 303 to start an initialization sequence processing (S603). The recognition processing unit 303 issues a recognition command ACMD 41 within a predetermined time period from when the instruction is received. As a result, an initialization processing (S604) starts, and when this initialization processing completes, the recognition processing of the SD memory card completes.
FIG. 4 is a diagram showing a relationship between a supply voltage and recognition processing time with respect to a conventional SD memory card. As described above, conventionally, as soon as the SD memory card is inserted into the SD slot, an electric power supply to the SD memory card starts. When the power-up time, which goes on until the supply voltage reaches the minimum supply voltage, elapses, the ramp-up time, which goes on until the supply voltage reaches the bus supply voltage, starts. When the ramp-up time elapses (or when the initialization sequence processing completes), the ACMD 41 is sent to the SD memory card, and the initialization processing starts. When the initialization processing completes, the mobile terminal recognizes that the inserted card is the SD memory card. From this time on, it is possible to access the SD memory card.
As described above, it is common that the electric power supply to the SD memory card starts when the SD memory card is inserted into the mobile terminal. It is also common that once the electric power supply starts, the electric power supply continues in an electric power saving mode even when the SD memory card is not in use.